The proposed project will utilize the comprehensive dataset from the Vision in Preschoolers (VIP) Study, a multi-center, cross-sectional, two-phased study sponsored by the National Eye Institute, to address unanswered questions that are of clinical and public health importance in vision screening. The specific aims of this proposal do not include the major goals of the VIP Study, which were already accomplished and published. Instead, the proposed project involves the additional analysis of the VIP data to address the following important new aims, some of which were raised by experts during the National Eye Institute-sponsored Expert Panel Meeting in July 2005: (1) Evaluate the validity of noncycloplegic retinoscopy, Retinomax Autorefractor, SureSight Vision Screener, and Lea Symbols VA test for detecting VIP-defined hierarchical Group 1 conditions only (most severe), Group 1 &2 conditions (most and moderately severe), all VIP-targeted vision conditions, and for detecting each specific type of refractive error (myopia, hyperopia, astigmatism, and anisometropia) with various levels of severity, by using receiver operating characteristic (ROC) analysis. Make ROC results available to the public through an interactive, user- friendly website. (2) Examine the relation between anisometropia and unilateral amblyopia and between bilateral high refractive error and bilateral amblyopia, and the differences in their relation as a function of age of the child. (3) Determine the ethnic-specific prevalence of VIP-targeted vision conditions among Head Start preschool children. The VIP dataset is a unique resource to evaluate the operating characteristics of the best-performing vision screening tools that are now being used widely by organizations that conduct preschool vision screening, and to better understand vision conditions among preschoolers. The very large sample size (N=4,040), as well as the experience and high productivity of the VIP Study Group, support the feasibility and likelihood of high yield of the proposed project.